Taking a nap, we've seen time and again, is like rebooting your brain. But napping may be as much of an art as it is a science. The Wall Street Journal offers recommendations for planning your perfect nap, including how long to nap and when.

According to a growing body of research, napping is a smart thing to do. It can help refresh the…
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The sleep experts in the article say a 10-to-20-minute power nap gives you the best "bang for your buck," but depending on what you want the nap to do for you, other durations might be ideal:

For a quick boost of alertness, experts say a 10-to-20-minute power nap is adequate for getting back to work in a pinch.

For cognitive memory processing, however, a 60-minute nap may do more good, Dr. Mednick said. Including slow-wave sleep helps with remembering facts, places and faces. The downside: some grogginess upon waking.

Finally, the 90-minute nap will likely involve a full cycle of sleep, which aids creativity and emotional and procedural memory, such as learning how to ride a bike. Waking up after REM sleep usually means a minimal amount of sleep inertia, Dr. Mednick said.

In addition to those recommendations, one surprising suggestion is to sit slightly upright during your nap, because it will help you avoid a deep sleep. And if you find yourself dreaming during your power naps, it may be a sign you're sleep deprived.